Car wouldn't start. Got a boost from another vehicle to start. Drove an hour, shut car off, then tried to start - nothing. Turns out the car ran only on the alternator. Its like the battery is totally dead.

Long story short: keep blowing the 100A slo-blo fuse that is connected at the battery in the trunk. There is a short. It is not the battery cables from original battery location to the trunk. It is somewhere between the original positive terminal and ground - somewhere in the original wiring.

I'm ruling out the alternator as the problem since the car ran fine on it alone. And nothing started on fire and everything worked correctly once the car was running on the alternator after boosting.

Ideas? Starter soleniod or starter short? Or is it an alternator short somehow?

 

Any flashing lights on the dashboard when the engine is running ?
Test the voltage at the alternator versus at the battery, check continuity from the battery to the alternator and starter.

 

When you jumped the car did you use the posts you made under the hood? If the Alt was grounding out I would think that jumping the car anywhere would not have worked. If the starter was bad it wouldve acted funny when it DID start.

Which leads me to wonder if your battery cable running to the trunk has rubbed something or gotten grounded out somehow. Because if its working from the posts in the engine bay the stock harness should be fine. And if your blowing the fuse on the trunk battery then the only connecting piece would be that positive wire running to the trunk.

IDK maybe Im not thinking about something. I havent had coffee yet...

 

Thanks for the ideas guys.

Yes I boosted and started the car from the terminals in the front.

I will double-check the cables from original battery location to trunk. Logic seems to say this is where the short is, but the ohmmeter did show infinite resistance from the positive trunk cable to ground - I'll wiggle that cable around this time. Darn, I try to be so meticulous with my custom work.

And I'll check the cables from battery to starter and to alternator again. The short must be there somewhere(?). If good, then I'll install another slo-blo fuse and see if it craps out immediately again (8$ a pop!).

Is it possible for the alternator diodes to fail in such a way as to connect the battery straight to ground?

 

Had any luck?

 

Nick, the diodes in the rectifier are connected to ground, it's possible you have a short through the alternator...

 

Yesterday I finally was able to escape from family and work obligations to tend to the RA.

Tore car apart, checked for positive cables wearing through or touching to ground somehow. No short anywhere. Took off starter solenoid to examine, checked external alternator connections - no shorts.

Alriiiiight then. Hook up new size 51 battery in trunk. New slo-blo 100A fuse installed. Also disconnect the alternator-to-battery wire before I try to start the car in case it is diodes shorting out. Turn key, lights go on, car starts and idles - yay! Turn car off, reconnect alternator, key on, car starts and idles. I'm confused but I'll take it!

Final thoughts on what might have caused the problem. Car was out in very heavy rains for two days, maybe alternator soaked and shorted? Or the PC680 somehow generated huge currents as if it was shorted? Man, problems you can only "see" by mental visualization are disturbing.

 

Weird....

At least its working now though!